1. Field of the Invention
The present invention relates to a power supply system and a display apparatus, and more particularly, to a power supply system which processes a dynamic charging operation to shorten a charging period for driving a display apparatus.
2. Description of the Prior Art
During portable electronic devices rapidly developing, thinner products with energy saving and carbon reduction are much more popular in the market. For example, flexible printed circuit boards (PCBs) in the thin film transistor liquid crystal display (TFT LCD) are installed multiple passive elements, e.g. capacitors or diodes. For the purpose of pursuing thinner and lighter products to effectively reduce the size of the flexible PCBs, these passive elements are designed to be disposed/moved inside a driving chip of the TFT LCD, and a load module corresponding to the driving chip is demonstrated as a resistor-capacitor model shown in FIG. 1A. When the load module forms as a gate type, a capacitance value is around 20 pF; when the load module forms as a source type, a capacitance value is around 30-60 pF, wherein both types of the load modules with different capacitance values correspond to a load charging period shown in FIG. 1B.
Please refer to FIG. 2A and FIG. 2B, wherein FIG. 2A illustrates a schematic diagram of a conventional two-times-voltage charging pump power supply system 2, and FIG. 2B is a schematic diagram of a charging pump module 20 in FIG. 2A. As shown in FIG. 2A and FIG. 2B, the two-times-voltage charging pump power supply system 2 comprises a charging pump module 20, an amplifying module 22 and a load module 23 (such as an equivalent load circuit of a display panel), and the charging pump module 20 comprises transistor switches M1-M8, flying capacitor units C1 and C2 and a storage capacitor Cs. Preferably, the charging pump module 20 utilizes conduction signals KA, KB, XA (an inversion signal of KA) and XB (an inversion signal of KB) to correspondingly conduct the transistor switches M1-M8 and utilizes a voltage VDD for charging the flying capacitor units C1 and C2, so as to output a charging voltage VS. Further, the amplifying module 22 is operated to amplify a voltage source, such as the charging voltage VS, to be outputted as an amplifying voltage, and the amplifying voltage is transmitted to the load module 24 to process the charging operation for the equivalent resistor-capacitor circuit.
However, in the prior art, the flying capacitor units C1 and C2 or the storage capacitor Cs have fixed capacitance values. If a user utilizes an elevated clock signal clk for shortening a charging period, the charging pump module 20 may continuously output an exceeding charging current to charge the equivalent resistor-capacitor circuit via the elevated clock signal clk while the equivalent resistor-capacitor circuit of the load module 24 is almost to finish the charging operation within the load charging period, which may violate the purpose of energy saving. If the user lowers the clock signal clk, the fixed capacitance values of the flying capacitor units C1 and C2 and the storage capacitor Cs may result in more generation of noises of the charging voltage VS, to significantly disturb an output voltage level of the charging voltage VS.
Therefore, it has become an important issue to provide another circuit designs for the conventional charging pump module, to adaptively turn on or turn off a plurality of flying capacitor units in the charging pump module, so as to output an adjustable charging voltage for adaptively shortening the load charging period.